Cellular communication systems continue to grow in popularity and have become an integral part of both personal and business communications. Cellular telephones allow users to place and receive phone calls most anywhere they travel. Moreover, as cellular telephone technology is advanced, so too has the functionality of cellular devices. For example, many cellular devices now incorporate Personal Digital Assistant (PDA) features such as calendars, address books, task lists, calculators, memo and writing programs, etc. These multi-function devices usually allow users to wirelessly send and receive electronic mail (email) messages and access the internet via a cellular network and/or a wireless local area network (WLAN), for example.
Cellular devices have radio frequency (RF) processing circuits and receive or transmit radio communications signals typically using modulation schemes. For example, one particularly advantageous modulation scheme is a Quadrature modulation, which may be used in third and fourth generation cellular transceivers. Quadrature modulation and demodulation circuits may create linearity issues with power amplifiers and sometimes suffer poor antenna match. This can cause some degradation of total radiated power (TRP) and raise harmonic interference issues because of the greater non-linearity of a power amplifier.
Another modulation approach is a polar modulation, which may be more power efficient than Quadrature modulation approaches. Nevertheless, cellular devices that use polar modulation circuits may become overly complex when designed to transmit large bandwidth signals, for example, third and fourth generation cellular transceiver signals. For example, broadband applications in polar modulation circuits may incur a complicated phase locked loop (PLL) design, onerous expansion of signal bandwidth during polar modulation processing, and a difficult power amplifier design. On the other hand, Quadrature modulation devices may more readily handle broadband applications, but also may consume more power.